About The Common PCB Surface Treatment.
A PCB surface finish is a coating between a component and a bare board PCB. It is applied for two basic reasons: to ensure solderability, and to protect exposed copper circuitry. As there are many types of surface finishes, selecting the right one is no easy task, especially as surface mounts have become more complex and regulations such as RoHS and we have changed industry standards.
After your PCB design, the next step is put your Gerber files to PCB fab to making. And when submiting orders, there is a choice for surface treatment. In ALLPCB ( a topspeed PCB prototype manufacturer, offer full service for PCB, PCBA, SMT stencil), webesite, they are 4 choice for surface treatment: HASL with lead, HASL lead free, Immersion Gold, and OSP
Let us see a simply introduce for the PCB surface treatment, that is showed in ALLPCB site.
1. Lead vs. Lead free
For decades HASL was one of the most popular surface finish choices. Yet, in recent years, manufacturers have realized its limitations. While a surface finish may be low cost and robust, fundamental changes in the PCB industry—namely, the rise complex surface mount technology—have exposed its shortcomings. HASL leaves uneven surfaces and is not suitable for fine pitch components. Although it does come in lead-free, there are other lead-free options which will likely make more sense for a high-reliability product.
2. OSP (Organic Solderability Preservative)
OSP is a water-based, organic surface finish that is typically used for copper pads. It selectively bonds to copper and protects the copper pad before soldering. OSP is environmentally friendly, provides a coplanar surface, is lead-free, and requires low equipment maintenance. However, it’s not as robust as HASL and can be sensitive while handling.
3. ENIG is quickly becoming the most popular surface finish in the industry. It’s a double layer metallic coating, with nickel acting as both a barrier to the copper and a surface to which components are soldered. A layer of gold protects the nickel during storage. ENIG is an answer to major industry trends such as lead-free requirements and rise of complex surface components (especially BGAs and flip chips), which require flat surfaces. But ENIG can be expensive, and at times can result in what is commonly known as “black pad syndrome,” a buildup of phosphorous between the gold and nickel layers that can result in fractured surfaces and faulty connections.
In PCB industry,HASL and HASL lead free is most widely used in surface finish in ALLPCB, PCBwin, PCBcart,
as the HASL or HASL lead free for their cost effective advantage. It mainly because of following reason:
–The low cost: normally it is 10%-15% cheaper with HASL than that with other surface finish
–Fast delivery: HASL is most commonly used in pcb filed and thus with the best production time.
–Quality control: It is more stable and easier to control the quality during production.